The present invention relates to a pigment composition which shows excellent flowability and stability with time, when used for a gravure ink, a flexographic ink or an offset ink, and whose printed matter shows an excellent gloss, clearness, color strength and migrationfastness, and an ink composition using the same.
Phthalocyanine type pigments have a clear color tone and high color strength and are excellent in various resistances such as weather fastness or chemical resistance, so that they are used in a wide range of uses. However, since they are hard to disperse in most cases, the value of a product is impaired in some uses.
Particularly, when a phthalocyanine type pigment is used in a gravure ink, a flexographic ink or an offset ink, an obtained ink tends to have a high viscosity, since it is required to disperse the pigment in a vehicle for an ink such that the pigment has a relatively fine particle diameter of 0.1 xcexcm or less therein. Therefore, it is difficult to take out of the ink from an ink dispersion equipment and to transport it. In some cases, the ink undergoes gelation during storage and becomes unusable. Further, the pigment undergoes agglomeration in the ink and an agglomerate precipitates in some cases. Further, concerning a printed matter, decreases in gloss, clearness and color strength occur in some cases.
Various methods have been proposed for solving various problems like above. As a particularly effective method, there is a method in which an alkaline earth metal salt or organic amine salt of a copper phthalocyanine sulfonic acid is mixed with a phthalocyanine type pigment, as shown in publications of U.S. Pat. No. 2,526,345, JP-B-39-28884, JP-B-40-4143 and JP-B-3-132231. However, the flowability of an ink is still insufficient and a phenomenon occurs in which the viscosity of ink gradually increases during storage. In an ink-manufacturing system including passing the stage of a high-concentrated pigment dispersion, which system is widely adopted in ink makers, in particular, the production of an ink is interfered with in many cases, since the viscosity of the high-concentrated pigment dispersion is too high.
It is an object of the present invention to provide a pigment composition which shows excellent flowability and stability with time, when used for a gravure ink, a flexographic ink or an offset ink, and whose printed matter shows an excellent gloss, clearness, color strength and migrationfastness, and an ink composition using the same.
It is another object of the present invention to provide a pigment composition which is particularly excellent in flowability, i.e. low in viscosity, and has a little viscosity increase with time, and an ink composition using the same.
The present invention provides a pigment composition formed of a phthalocyanine type pigment and a compound of the formula (1),
P-[SO3xe2x88x92.Fen+/n]mxe2x80x83xe2x80x83(1)
wherein P is a metal-free or metal phthalocyanine residue which may be substituted with a chlorine atom, a bromine atom or both of them, n is 2 or 3 and m is a number of 1 to 4.
The present invention further provides a pigment composition according to the above, wherein the amount of the compound of the formula (1) per 100 parts by weight of the phthalocyanine type pigment is 0.1 to 30 parts by weight.
The present invention further provides an ink composition composed of the above pigment composition and a vehicle for an ink.